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<div class="branding-box"> <a href="/wiki/Main_Page"> <span><img src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" alt="Wikipedia" width="120" height="18" style="width: 7.5em; height: 1.125em;"/> </span> </a> </div> <form action="/w/index.php" method="get" class="minerva-search-form"> <div class="search-box"> <input type="hidden" name="title" value="Special:Search"/> <input class="search skin-minerva-search-trigger" id="searchInput" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f"> <span class="search-box-icon-overlay"><span class="minerva-icon minerva-icon--search"></span> </span> </div> <button id="searchIcon" class="cdx-button cdx-button--size-large cdx-button--icon-only cdx-button--weight-quiet skin-minerva-search-trigger"> <span class="minerva-icon minerva-icon--search"></span> <span>Search</span> </button> </form> <nav class="minerva-user-navigation" aria-label="User navigation"> </nav> </div> </header> <main id="content" class="mw-body"> <div class="banner-container"> <div id="siteNotice"></div> </div> <div class="pre-content heading-holder"> <div class="page-heading"> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Punycode</span></h1> <div class="tagline"></div> </div> <ul id="p-associated-pages" class="minerva__tab-container"> <li class="minerva__tab selected"> <a class="minerva__tab-text" href="/wiki/Punycode" rel="" data-event-name="tabs.subject">Article</a> </li> <li class="minerva__tab "> <a class="minerva__tab-text" href="/wiki/Talk:Punycode" rel="discussion" data-event-name="tabs.talk">Talk</a> </li> </ul> <nav class="page-actions-menu"> <ul id="p-views" class="page-actions-menu__list"> <li id="language-selector" class="page-actions-menu__list-item"> <a role="button" href="#p-lang" data-mw="interface" data-event-name="menu.languages" title="Language" class="cdx-button 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cdx-button--weight-quiet edit-page menu__item--page-actions-edit"> <span class="minerva-icon minerva-icon--edit"></span> <span>Edit</span> </a> </li> </ul> </nav>  <div id="mw-content-subtitle"></div> </div> <div id="bodyContent" class="content"> <div id="mw-content-text" class="mw-body-content"><script>function mfTempOpenSection(id){var block=document.getElementById("mf-section-"+id);block.className+=" open-block";block.previousSibling.className+=" open-block";}</script><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><section class="mf-section-0" id="mf-section-0"> <p><b>Punycode</b> is a representation of <a href="/wiki/Unicode" title="Unicode">Unicode</a> with the limited <a href="/wiki/ASCII" title="ASCII">ASCII</a> character subset used for Internet <a href="/wiki/Hostname" title="Hostname">hostnames</a>. Using Punycode, host names containing Unicode characters are transcoded to a subset of ASCII consisting of letters, digits, and hyphens, which is called the letter–digit–hyphen (LDH) subset. For example, <i>München</i> (<a href="/wiki/German_language" title="German language">German</a> name for <a href="/wiki/Munich" title="Munich">Munich</a>) is encoded as <i>Mnchen-3ya</i>. </p><p>While the <a href="/wiki/Domain_Name_System" title="Domain Name System">Domain Name System</a> (DNS) technically supports arbitrary sequences of octets in domain name labels, the DNS standards recommend the use of the LDH subset of ASCII conventionally used for host names, and require that string comparisons between DNS domain names should be case-insensitive. The Punycode syntax is a method of encoding strings containing Unicode characters, such as <a href="/wiki/Internationalized_domain_name" title="Internationalized domain name">internationalized domain names</a> (IDNA), into the LDH subset of ASCII favored by DNS. It is specified in <a href="/wiki/IETF" class="mw-redirect" title="IETF">IETF</a> <a href="/wiki/Request_for_Comments" title="Request for Comments">Request for Comments</a> 3492.<sup id="cite_ref-rfc3492_1-0" class="reference"><a href="#cite_note-rfc3492-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <div id="toc" class="toc" role="navigation" aria-labelledby="mw-toc-heading"><input type="checkbox" role="button" id="toctogglecheckbox" class="toctogglecheckbox" style="display:none"><div class="toctitle" lang="en" dir="ltr"><h2 id="mw-toc-heading">Contents</h2><span class="toctogglespan"><label class="toctogglelabel" for="toctogglecheckbox"></label></span></div> <ul> <li class="toclevel-1 tocsection-1"><a href="#Description"><span class="tocnumber">1</span> <span class="toctext">Description</span></a> <ul> <li class="toclevel-2 tocsection-2"><a href="#Separation_of_ASCII_characters"><span class="tocnumber">1.1</span> <span class="toctext">Separation of ASCII characters</span></a></li> <li class="toclevel-2 tocsection-3"><a href="#Encoding_the_non-ASCII_characters"><span class="tocnumber">1.2</span> <span class="toctext">Encoding the non-ASCII characters</span></a></li> <li class="toclevel-2 tocsection-4"><a href="#Variable-length_number_encoding"><span class="tocnumber">1.3</span> <span class="toctext">Variable-length number encoding</span></a></li> <li class="toclevel-2 tocsection-5"><a href="#ACE_prefix_for_internationalized_domain_names"><span class="tocnumber">1.4</span> <span class="toctext">ACE prefix for internationalized domain names</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-6"><a href="#Examples"><span class="tocnumber">2</span> <span class="toctext">Examples</span></a></li> <li class="toclevel-1 tocsection-7"><a href="#See_also"><span class="tocnumber">3</span> <span class="toctext">See also</span></a></li> <li class="toclevel-1 tocsection-8"><a href="#References"><span class="tocnumber">4</span> <span class="toctext">References</span></a></li> <li class="toclevel-1 tocsection-9"><a href="#External_links"><span class="tocnumber">5</span> <span class="toctext">External links</span></a></li> </ul> </div> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(1)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Description">Description</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=1" title="Edit section: Description" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-1 collapsible-block" id="mf-section-1"> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Technical plainlinks metadata ambox ambox-style ambox-technical" role="presentation"><tbody><tr><td class="mbox-text"><div class="mbox-text-span">This section <b>may be too technical for most readers to understand</b>.<span class="hide-when-compact"> Please <a class="external text" href="https://en.wikipedia.org/w/index.php?title=Punycode&action=edit">help improve it</a> to <a href="/wiki/Wikipedia:Make_technical_articles_understandable" title="Wikipedia:Make technical articles understandable">make it understandable to non-experts</a>, without removing the technical details.</span> <span class="date-container"><i>(<span class="date">September 2024</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>As stated in RFC 3492, "Punycode is an instance of a more general algorithm called <i>Bootstring</i>, which allows strings composed from a small set of 'basic' code points to uniquely represent any string of code points drawn from a larger set." Punycode defines parameters for the general Bootstring algorithm to match the characteristics of Unicode text. This section demonstrates the procedure for Punycode encoding, using the example of the string "bücher" (<i>Bücher</i> is <a href="/wiki/German_language" title="German language">German</a> for <i>books</i>), which is translated into the label "bcher-kva". </p><p>To make the encoding and decoding algorithms simple, no attempt has been made to prevent some encoded values from encoding inadmissible Unicode values: however, these should be checked for and detected during decoding. </p><p>Punycode is designed to work across all scripts, and to be self-optimizing by attempting to adapt to the character set ranges within the string as it operates. It is optimized for the case where the string is composed of zero or more ASCII characters and in addition characters from only one other script system, but will cope with any arbitrary Unicode string. Note that for DNS use, the domain name string is assumed to have been normalized using <a href="/wiki/Nameprep" title="Nameprep">nameprep</a> and (for <a href="/wiki/Top-level_domain" title="Top-level domain">top-level domains</a>) filtered against an officially registered language table before being punycoded, and that the DNS protocol sets limits on the acceptable lengths of the output Punycode string. </p> <div class="mw-heading mw-heading3"><h3 id="Separation_of_ASCII_characters">Separation of ASCII characters</h3><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=2" title="Edit section: Separation of ASCII characters" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div> <p>First, all <a href="/wiki/ASCII" title="ASCII">ASCII</a> characters in the string are copied from input to output, skipping over any other characters. For example, "bücher" is copied to "bcher". If any characters were copied, i.e. if there was at least one ASCII character in the input, an ASCII hyphen is appended to the output (e.g., "bücher" → "bcher-", but "ü" → ""). </p><p>Note that hyphens are themselves ASCII characters. Thus, they can be present in the input and, if so, they will be copied to the output. This causes no ambiguity: if the output contains hyphens, the one that got added is always the last one. It marks the end of the ASCII characters. </p> <div class="mw-heading mw-heading3"><h3 id="Encoding_the_non-ASCII_characters">Encoding the non-ASCII characters</h3><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=3" title="Edit section: Encoding the non-ASCII characters" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div> <p>The non-ASCII characters are sorted by Unicode value, lowest first (if a character occurs more than once they are sorted by position). Each is then encoded as a single number. This single number defines both the location to insert the character at and which character to insert. </p> <ul><li><span class="texhtml mvar" style="font-style:italic;">i</span> is an index into the result to insert the code at, starting at 0 (for insertion at the start).<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2024)">citation needed</span></a></i>]</sup></li> <li><span class="texhtml mvar" style="font-style:italic;">n</span> is the number of possible insertion points (current length of the result plus one).</li> <li><span class="texhtml mvar" style="font-style:italic;">j</span> is the Unicode code point to insert minus 127.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2024)">citation needed</span></a></i>]</sup></li></ul> <p>The encoded number is <span class="texhtml"><i>n</i> × <i>j</i> + <i>i</i></span>. By dividing by <span class="texhtml mvar" style="font-style:italic;">n</span> and also getting the remainder, a decoder can determine <span class="texhtml mvar" style="font-style:italic;">j</span> and <span class="texhtml mvar" style="font-style:italic;">i</span>. </p><p>There are six possible places to insert a character in the string "bcher" (including before the first character and after the last one). There are 124 code points between the last ASCII code point (127 = <style data-mw-deduplicate="TemplateStyles:r886049734">.mw-parser-output .monospaced{font-family:monospace,monospace}</style><span class="monospaced">0x7F</span>, the end of ASCII) and <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">ü</span> (code point 252 = <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">0xFC</span>, see Unicode's <a href="/wiki/Latin-1_Supplement_(Unicode_block)" class="mw-redirect" title="Latin-1 Supplement (Unicode block)">Latin-1 Supplement</a>). The <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">ü</span> is inserted at position 1, after the <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">b</span>. Thus the encoder will add the number <span class="nowrap">(6 × 124) + 1 = 745</span>, and the decoder can retrieve these by <span class="nowrap">⌊745 ÷ 6⌋ = 124</span> and <span class="nowrap">745 mod 6 = 1</span>. </p><p>These numbers are strictly increasing. For the second and subsequent inserted characters, the difference between the number and the previous one is written. </p><p>The number is encoded using the letters <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">a</span> through <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">z</span> and the digits <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">0</span> through <span class="nounderlines" style="border: 1px solid var(--border-color-muted,#ddd); color: var(--color-base); background-color: var( --background-color-neutral-subtle, #fdfdfd); padding: 1px 1px;">9</span>. It is not base-36 but a more complex scheme described below, which allows the numbers to be concatenated, with nothing separating them. </p> <div class="mw-heading mw-heading3"><h3 id="Variable-length_number_encoding">Variable-length number encoding</h3><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=4" title="Edit section: Variable-length number encoding" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div> <p>Punycode uses <a href="/wiki/Numeral_system#Generalized_variable-length_integers" title="Numeral system">generalized variable-length integers</a> to represent these values. For example, this is how "kva" is used to represent the code number 745: </p> <blockquote> <p>A number system with <a href="/wiki/Endianness#Detailed_description" title="Endianness">little-endian ordering</a> is used which allows variable-length codes without separate delimiters: a digit lower than a threshold value marks that it is the most-significant digit, hence the end of the number. The threshold value depends on the position in the number and also on previous insertions, to increase efficiency. Correspondingly the weights of the digits vary. </p><p>In this case a number system with 36 symbols is used, with the <a href="/wiki/Case_sensitivity" title="Case sensitivity">case-insensitive</a> 'a' through 'z' equal to the decimal numbers 0 through 25, and '0' through '9' equal to the decimal numbers 26 through 35. Thus "kva", corresponds to the decimal number string "10 21 0". </p> </blockquote> <p>To decode this string of symbols, a sequence of thresholds will be needed, in this case it's (1, 1, 26, 26, ...).<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The weight (or <a href="/wiki/Place_value" class="mw-redirect" title="Place value">place value</a>) of the least-significant digit is always 1: 'k' (=10) with a weight of 1 equals 10. After this, the weight of the next digit depends on the first threshold: generally, for any <i>n</i>, the weight of the (<i>n</i>+1)-th digit is <i>w</i> × (36 − <i>t</i>), where <i>w</i> is the previous weight and <i>t</i> is the threshold of the <i>n</i>-th digit. So in this case, the second symbol has a place value of 36 minus the previous threshold value of 1, which equals 35. Therefore, the sum of the first two symbols 'k' (=10) and 'v' (=21) is 10 × 1 + 21 × 35. Since the second symbol is not less than its threshold value of 1, there is more to come. However, since the third symbol in this example is 'a' (=0), we may ignore calculating its weight. Therefore, "kva" represents the decimal number (10 × 1) + (21 × 35) = 745. </p><p>Number 745 will be encoded as 10 + 21 × 35 + 0 (base 35 used for second digit, the most significant digit 0 needed as terminator), 10 → 'k', 21 → 'v', 0 → 'a', so "bücher" → "bcher-kva". </p><p>The thresholds themselves are determined for each successive encoded character by an algorithm keeping them between 1 and 26 inclusive.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The case can then be used to provide information about the original case of the string.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>Because special characters are sorted by their code points by encoding algorithm, for the insertion of a second special character in "bücher", the first possibility is "büücher" with code "bcher-kvaa", the second "bücüher" with code "bcher-kvab", etc. After "bücherü" with code "bcher-kvae" comes codes representing insertion of ý, the Unicode character following ü, starting with "ýbücher" with code "bcher-kvaf" (different from "übücher" coded "bcher-jvab"), etc. </p> <div class="mw-heading mw-heading3"><h3 id="ACE_prefix_for_internationalized_domain_names">ACE prefix for internationalized domain names</h3><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=5" title="Edit section: ACE prefix for internationalized domain names" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Internationalized_domain_name" title="Internationalized domain name">Internationalized domain name</a></div> <p>To prevent hyphens in non-international domain names from triggering a Punycode decoding, the string <code>xn--</code> is prepended to Punycode sequences in internationalized domain names. This is called ACE (ASCII Compatible Encoding).<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>Thus the domain name "bücher.tld" would be represented in a URL as "xn--bcher-kva.tld". </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(2)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Examples">Examples</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=6" title="Edit section: Examples" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-2 collapsible-block" id="mf-section-2"> <p>The following table shows examples of Punycode encodings for different types of input.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable"> <tbody><tr> <th>Input</th> <th>Punycode</th> <th>Description </th></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"></span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"></span></td> <td>The empty string. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">a</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">a-</span></td> <td>Only <a href="/wiki/ASCII" title="ASCII">ASCII</a> characters, one, lowercase. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">A</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">A-</span></td> <td>Only ASCII characters, one, uppercase. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">3</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">3-</span></td> <td>Only ASCII characters, one, a digit. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">-</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">--</span></td> <td>Only ASCII characters, one, a hyphen. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">--</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">---</span></td> <td>Only ASCII characters, two hyphens. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">London</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">London-</span></td> <td>Only ASCII characters, more than one, no hyphens. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Lloyd-Atkinson</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Lloyd-Atkinson-</span></td> <td>Only ASCII characters, one hyphen. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">This has spaces</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">This has spaces-</span></td> <td>Only ASCII characters, with spaces. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">-> $1.00 <-</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">-> $1.00 <--</span></td> <td>Only ASCII characters, mixed symbols. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Б</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">d0a</span></td> <td>No ASCII characters, one <a href="/wiki/%C6%82" title="Ƃ">Cyrillic character</a>. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">ü</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">tda</span></td> <td>No ASCII characters, one <a href="/wiki/Latin-1_Supplement" title="Latin-1 Supplement">Latin-1 Supplement</a> <a href="/wiki/%C3%9C" title="Ü">character</a>. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">α</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">mxa</span></td> <td>No ASCII characters, one <a href="/wiki/Alpha" title="Alpha">Greek character</a>. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">例</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fsq</span></td> <td>No ASCII characters, one <a href="/wiki/CJK_characters" title="CJK characters">CJK</a> character. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">😉</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">n28h</span></td> <td>No ASCII characters, one <a href="/wiki/Emoji" title="Emoji">emoji</a> character. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">αβγ</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">mxacd</span></td> <td>No ASCII characters, more than one character. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">München</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Mnchen-3ya</span></td> <td>Mixed string, with one character that is not an ASCII character. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Mnchen-3ya</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Mnchen-3ya-</span></td> <td>Double-encoded Punycode of "München". </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">München-Ost</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Mnchen-Ost-9db</span></td> <td>Mixed string, with one character that is not ASCII, and a hyphen. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span class="nowrap">Bahnhof München-Ost</span></span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">Bahnhof Mnchen-Ost-u6b</span></td> <td>Mixed string, with one space, one hyphen, and one character that is not ASCII. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">abæcdöef</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">abcdef-qua4k</span></td> <td>Mixed string, two non-ASCII characters. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">правда</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">80aafi6cg</span></td> <td><a href="/wiki/Russian_language" title="Russian language">Russian</a>, without ASCII. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">ยจฆฟคฏข</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">22cdfh1b8fsa</span></td> <td><a href="/wiki/Thai_language" title="Thai language">Thai</a>, without ASCII. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">도메인</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">hq1bm8jm9l</span></td> <td><a href="/wiki/Korean_language" title="Korean language">Korean</a>, without ASCII. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">ドメイン名例</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">eckwd4c7cu47r2wf</span></td> <td><a href="/wiki/Japanese_language" title="Japanese language">Japanese</a>, without ASCII. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">MajiでKoiする5秒前</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span class="nowrap">MajiKoi5-783gue6qz075azm5e</span></span></td> <td>Japanese with ASCII. </td></tr> <tr> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">「bücher」</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">bcher-kva8445foa</span></td> <td>Mixed non-ASCII scripts (Latin-1 Supplement and CJK). </td></tr> </tbody></table> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(3)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="See_also">See also</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=7" title="Edit section: See also" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-3 collapsible-block" id="mf-section-3"> <ul><li><a href="/wiki/Emoji_domain" title="Emoji domain">Emoji domain</a></li> <li><a href="/wiki/UTF-5" class="mw-redirect" title="UTF-5">UTF-5</a></li> <li><a href="/wiki/UTF-6" class="mw-redirect" title="UTF-6">UTF-6</a></li> <li><a href="/wiki/Website_spoofing" title="Website spoofing">Website spoofing</a></li></ul> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(4)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="References">References</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=8" title="Edit section: References" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-4 collapsible-block" id="mf-section-4"> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-rfc3492-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-rfc3492_1-0">^</a></b></span> <span class="reference-text">RFC <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc3492">3492</a>, <i>Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDN)</i>, A. Costello, The Internet Society (March 2003)</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">This is true for the first encoded character (or, in terms of RFC 3492, the first "delta"): see RFC 3492, Sec. 6.</span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">RFC 3492, Secs. 3.4, 5.</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">RFC 3492, App. A.</span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFInternet_Assigned_Numbers_Authority2003" class="citation web cs1"><a href="/wiki/Internet_Assigned_Numbers_Authority" title="Internet Assigned Numbers Authority">Internet Assigned Numbers Authority</a> (2003-02-14). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100427154004/http://www.atm.tut.fi/list-archive/ietf-announce/msg13572.html">"Completion of IANA Selection of IDNA Prefix"</a>. <i>www.atm.tut.fi</i>. Archived from <a rel="nofollow" class="external text" href="http://www.atm.tut.fi/list-archive/ietf-announce/msg13572.html">the original</a> on 2010-04-27<span class="reference-accessdate">. Retrieved <span class="nowrap">2017-09-22</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.atm.tut.fi&rft.atitle=Completion+of+IANA+Selection+of+IDNA+Prefix&rft.date=2003-02-14&rft.au=Internet+Assigned+Numbers+Authority&rft_id=http%3A%2F%2Fwww.atm.tut.fi%2Flist-archive%2Fietf-announce%2Fmsg13572.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APunycode" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text">The Punycode in this table was created using the builtin codec "punycode" of the <a href="/wiki/Python_(programming_language)" title="Python (programming language)">Python programming language</a> version 3.8 (<code>s.encode("punycode")</code>). See <a href="/wiki/Talk:Punycode#More_examples_are_needed,_especially_pure_ASCII_examples_and_corner_cases" title="Talk:Punycode">talk page</a>.</span> </li> </ol></div></div> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(5)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="External_links">External links</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Punycode&action=edit&section=9" title="Edit section: External links" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-5 collapsible-block" id="mf-section-5"> <ul><li><a rel="nofollow" class="external text" href="https://www.rfc-editor.org/rfc/rfc3492.txt">IETF Punycode standard</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070129082116/http://demo.icu-project.org/icu-bin/idnbrowser">ICU IDNA Demonstration</a> An online demonstration of how <a href="/wiki/International_Components_for_Unicode" title="International Components for Unicode">ICU</a> performs IDN operations</li> <li><a rel="nofollow" class="external text" href="https://www.mozilla.org/projects/security/tld-idn-policy-list.html">List of TLDs considered by the Mozilla developers to have an effective anti-spoofing policy for name registration</a></li> <li><a rel="nofollow" class="external text" href="http://blogs.msdn.com/ie/archive/2006/07/31/684337.aspx">IDN and Punycode in IE7</a></li> <li><a rel="nofollow" class="external text" href="https://www.charset.org/punycode.php">Simple Punycode converter</a></li></ul>    </section></div> <noscript><img src="https://login.m.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1&mobile=1" alt="" width="1" height="1" style="border: none; position: 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class="read-more-container"></div> </div> <div id="p-lang"> <h4>Languages</h4> <section> <ul id="p-variants" class="minerva-languages"></ul> <ul class="minerva-languages"><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Punycode" title="Punycode – Catalan" lang="ca" hreflang="ca" data-title="Punycode" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Punycode" title="Punycode – Czech" lang="cs" hreflang="cs" data-title="Punycode" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Punycode" title="Punycode – German" lang="de" hreflang="de" data-title="Punycode" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Punycode" title="Punycode – Spanish" lang="es" hreflang="es" data-title="Punycode" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Punycode" title="Punycode – French" lang="fr" hreflang="fr" data-title="Punycode" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%93%A8%EB%8B%88%EC%BD%94%EB%93%9C" title="퓨니코드 – Korean" lang="ko" hreflang="ko" data-title="퓨니코드" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Punycode" title="Punycode – Indonesian" lang="id" hreflang="id" data-title="Punycode" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Punycode" title="Punycode – Italian" lang="it" hreflang="it" data-title="Punycode" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/Punycode" title="Punycode – Japanese" lang="ja" hreflang="ja" data-title="Punycode" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Punycode" title="Punycode – Occitan" lang="oc" hreflang="oc" data-title="Punycode" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Punycode" title="Punycode – Polish" lang="pl" hreflang="pl" data-title="Punycode" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Punycode" title="Punycode – Portuguese" lang="pt" hreflang="pt" data-title="Punycode" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li 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